Gas fired vacuum furnace



Jan. 19, 1965 v. R. TRoGLloNE ETAL. 3,166,305

. @As FIRED VACUUM FURNACE:

Filed June 25. 1961 2 Sheets-Sheet 1 Jan. 19, 1965 v. R. 'roGLloNE ETAL 3,156,305'

GAs FIRED vAcuuM FURNACE 2 Sheets-Sheet 2 Filed June 23. 1961 y" l? INVENTolgs:

l n i z@ W' Koi/L United States Patent O 3,166,305 GAS FIRED VACUUM FURNACE Vincent R. Troglione, Jonathan Smith, and Willard Roth,

all of Meadville, Pa., assignors to Sunbeam Corporation, Chicago, Ill., a corporation of Illinois Filed .lune 23, 1961, Ser. No. 119,215

6 Claims. (Cl. 263-41) This invention relates generally to gas tired furnaces, and more particularly, to vacuum furnaces.

In recent years there has been an increased demand for furnaces in which parts may be heated in a vacuum to high temperatures. There are a number of problems associated with heating of material in a vacuum which have not been satisfactorily solved by the prior art vacuum furnaces. Most of the prior art furnaces are unsuited to production applications in which the work charge must be heated quickly in a vacuum tight enclosure to a desired temperature and then cooled quickly prior to removal from the furnace.

It is conventional to employ radiation shields in connection with vacuum furnaces to concentrate the heat in the portion of the furnace containing the work charge. The necessity for a well sealed enclosure for the work charge as well as for radiation shields has produced furnaces which are difficult to load and unload. It would be desirable, therefore, to have a vacuum furnace in which the pressure tight enclosure may be easily opened and in which easy access may be had to the interior of the enclosure where the work charge is supported.

To withstand the high temperatures and pressures required in vacuum furnace applications, it is well known to use heavy walled retorts fabricated of alloys which retain their strength at high temperature. With the work charge enclosed in such a retort, the rapid heating of the work is more difficult than in a conventional furnace in which the heating means may radiate directly to the Work. In some instances this problem has been solved by placing electrical heating elements within the retort in-close proximity to the work. This solution has many drawbacks since it increases the size of the retort and complicates its strucbe suitable for a gas fired furnace inasmuch as the gas burner could not be placed within the vacuum enclosure.l

It would be desirable, therefore, to have a furnace in which gas fired means are provided to heatv rapidly a vacuum retort.

We have found that the rapid heating of the retort may best be accomplished byan arrangement in whichcombustion of the gas-air mixture takes place over a substantial area of the inner wall of the furnace adjacent the vacuum retort. While it is known in the art to pass a combustible gas through a refractoryV wall with combustion taking place along one wall surface, it has been necessary to provide elaborate sealing means to prevent leakage of gas through the refractory material to undesired areas. In addition, it has been necessary to form the refractory material in intricate shapes to assure proper combustion only on the inner wall and to assure proper cooling of the refractory material so combustion would not take place within or behind the wall. These problems encountered in the use of a porous wall type of gas burner have restricted its use considerably. s

It is, therefore, an object of the present invention to provide an improved vacuum furnace.

It is a further object of the invention to provide a vacuum `furnace having means for readily loading and removing the parts from the vacuum retort.

It is an additional object of the invention to provide a vacuum furnace having improvedzheating and cooling means whereby the vacuum retort of the furnace may be quickly heated and cooled. v f

It is a further object of the invention to provide a vacuum furnace having a simplified porous wall type of gas burner.

Further objects and advantages of the present invention will become apparent as the following description proceeds and the features of novelty which characterize the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

For a better understanding of the present invention reference may be had to the accompanying drawings in which:

FIG. l is a sectional View in elevation ofV an improved vacuum furnace constructed according to the present invention;

FIG. 2 is a plan view of the furnace of FIG. l with a portion thereof shown in section; and

ture considerably. In addition, such a solution would not s FIG. 3 is an enlarged View of the radiation shields employed in the furnace.

Briefly, the invention comprises a vacuum furnace in-.

cluding a vaccum-tight retort which is heated within an enclosure of refractory material, the combustion gases for the furnace passing through the porous walls of the re.

fractory enclosure with combustion taking place on the inner wall face. Air cooling means are providedvat` the upper and lower limits of the side walls of the refractory enclosure, such cooling means preventing leakage of the combustible material from the porous walls of the enclosure and serving to maintain the walls at a temperature elow the combustion temperature of the gas and to cool the furnace quickly at the end of the heat'treating period.

The vacuum retort comprises a cylindrical chamber closed at the top and having a removable closure positioned at the bottom opening thereof. The removable closure serves as a support for a fan and is movable downwardly from its position in sealing engagement with the opening in the retort to a position in which parts may be readily loaded thereon. Y p

Referring now to the drawings, there is illustrated in FIGS. l and 2 of the drawings a furnace generally designated by the reference numeral 11. The furnace 11 comprises vertical supports 12 which serve to support an enclosure 13. The furnace enclosure 13 is formed in the conventional manner having an outer cylindrical compartment 14 formed of -steel plate, which compartment surrounds a lining 15 of refractory material. The lining` 15 may be made up of individual rebrick or preformed slab.

The lining 15 includes a roof or cover portion 16 whichY drical refractory wall 17, there are formed a pair of peripherally extending passageways 17a which serve as cornbustion manifolds for the furnace. The annular passageways 17a are filled with rock wool designated by reference numeral 18. Because of the porous naturel of the rock wool 18, it permits the air-gas mixture to pass through the annular manifolds 17a readily but is effective as a fire checkin the event of a flash back through the porous walls of the furnace. The rock wool also acts as a filter for the incoming air-gas mixture. Y i 1 Extending around the;` outside of the cylindrical Vcornpartrncnt 14 adjacent the annular manifolds 17av are channel members 19 which are Vsuitably welded to the cylin- .aa-eases Y d drical Wall of the compartment 14 to form twoV sealed combustion manifolds 19a into which a mixture of gas and air is fed. A series of holes Mb are formed in the wall of compartment 14 permitting the combustible mixture to flow from the manifolds lga `formed by the channel V'members i9 into the passageways or manifolds E751 in the refractory wall f7. ln the preferred embodiment, a total of sixteen 7A@ inch diameter holes equally spaced around the periphery of the compartment llwere provided to permit the flow of the combustible mixture into each of the manifolds 17a.

It should be understood that the porosity of the refractory material i7 permits the air-gas mixture to pass from the annular manifolds F.7d through the wallsto the inside ofthe refractory lining 15 at which point combus- 'Vtion of the air-gas mixture occurs. While the refractory material 17 is porous and permits the gas mixture to pass upwardly and downwardly as well as inwardly, means are provided to prevent the leakage of the gas mixture in directions other than toward the interior of the refractory lining l5. The upper and lower edges of the cylindrical refractory wall 17 are sealed at their joints with the adjoining refractory portionsby an air setting cement. This cement prevents the passage of the air-gas mixture through these joints. Since it is virtually impossible to achieve a perfect gas seal with such sealing cement, additional means are provided to assure against the dangerous leakage of the air-gas mixture. y

Immediately below the cylindrical wall 17 there is a V.bottom.member 2h which completes the refractory lin- The bottom member Ztl is annular in shape havl ing a largeopeningZtla formed in the center thereof. The refractory member Ztl is supported on an annular plate 2l "which, is part of the steel plate compartment ld. The bottom Vmember 2@ cooperates with the cylindrical wall 17 and the coverV i6 to 'forni the refractory furnace lining ing 15.

15 in-towhicha vacuum reto-rt 23 is inserted upwardly through opening 20m The retort 23, which is ymade of partment 14 in the same manner as channel members i9 and which form cooling manifolds Metto conductair to the upper `and lower portions of the compartment ld.Vv

The refractory cover le is formed at its lower outer edge l with an annular shouldered portion leb which cooperates with the flange i411 andthe outer `wall of compartment 14" to form Lan annular passageway 22 within the refrac tory lining. A suitable fibrous, high temperature resistant? material such as rock wool is placed in passageway 22 to lter in air passing therethrough. The 'rock wool also affords' some thermal insulation during periods when no air is passed through the passageway 22. A plurality of holes 14C extend through the cylindrical wall of the steel plate compartment '1f-t to permit the passage of cooling` air from the channel 24 into the Vpassage Z2. Similarly, at the lower end of the furnace, the bottom member Ztl is formedV at its upper outer edge with a shouldered portion 2Gb which cooperates with 'the compartment la and a flange Mato'form an annular passageway 3l therein. A plurality: of holes ldd extenduthrough the wall of the Y compartment 14 permitting air Vto flow from the lower channel member 24 into the passageway 3l. t

' TheV air ksu'ppliedto the upper and lower channels 24 notonlyseives to'c'oolY the furnace walls during operation of the furnace and at the termination of a heating cycle Y kbut also is important in preventing leakage of the comlining l is substantially continuous across the cylindrical refractory wall 17 and heats'the interior thereof rapidly and uniformly. The use of upper and lower manifolds 11.762, i9@ permits some adjustment in the heating rate to compensate for the higher losses and heat storage in the bottom part of the chamber.

To cool the furnace, suitable valves are provided whereby the gas may be shut offand air passed through the combustion manifolds i761. The passage of such air through the refractory wall i7 results in extremely rapid and efficient cooling.

The rate of liow of the gas mixture through the porous walls .i7 of the refractory lining cools thewalls and prevents the walls from heating up to such a temperature that combustion might occur within the wall 17 or the combustion manifolds 17a The air passageways 22, 3l serve to reduce the temperature of the furnace walls at the cover le andthe bottom member 2li. In that no airgas mixture passes through the cover le or bottom member Ztl, there would be a tendency for the portions ad jacent the cylindrical wall ll7 to heat up toexcessively high temperatures. lHigh temperatures at these adjacent portions would create a possibility of flash backs 'through the upper and lower portions of cylindrical wall i7. It should be understood, therefore, that the air-delivered to the passageways Z2, 3f through themanifolds 24 serves the purposes of preventingleakage of the gas mixture up wardly or downwardly from the porous wall i7, of cooling the top and bottom of refractory wall i7 during operation, and of cooling the furnace down' after the 'heating cycle is terminated. l v

' To permit connection Vof a vacuum pump to the irlterior of the retort Y2GB, there is provided at the lower end ofthe retort an opening Zlib inthe side wall thereof. A

. vacuum conduit 25 is connected yto the retort 23 in comd pump may be connected.

bustion gases upwardly and downwardly through' the Y cylindrical walls 17.- rlhu's, 'by'pressurizi'ng the air in the A sealing flange 247 is secured to the lower end of the retort 23Yto facilitate the sealingthereof. The flange 27 has an annular groove 27a formed in the lower face thereof, VThe groove 27a4 is adapted to receive an O-ring sealing gasket 28 of silicone rubber or other high temperature kresilient material. On the upper face of the sealing yflange V27 there is mounted an inverted channel-V shaped member 29 which cooperates with the Vflange 27 to form a water cooling passageway 30. Suitable water connections -are provided to circulate.. cooling water through the passageway 36? to reduce the temperature of the sealing flange 27 and the-gasket 28.

To seal the bottom opening of the retort 23 there is provided a closure member 32 which also supports a circulating fan 33. The yclosurefrnember 32 is a large annular member having yan opening .32ak in theY center thereof through which a fan shaft 33a extends. Mounted on the upper end ofthe fan shaft is an impeller member 33h. The fan is of conventional construction being adapted for high temperature application by the inclusion of separate `water cooling means in the base thereof and having a sealed construction so that no air-rnay enter,

ing fan 33, but also supports a plurali-ty of radiation shields 34 which are positioned in the lower end of the retort 23. The purpose of the radiation shields 34 is to concentrate the heat in the upper high temperature portion of the retort 23 and limit heat transfer downwardly to the point at which the vacuum seal is made between the closure member 32 `and the bottom opening in the retort. In addition, it is desirable to maintain the circulating fan 33 at as low a temperature as possible. The radiation shields 34 are supported in vertically spaced relation by means of six posts 35 which are equally spaced around a supporting ange 36. The flange 36 is secured to the retort closure member 32 by means of bolts or the like while the posts 35 are received in holes in the iiange 36 and welded thereto.

As may best be seen in FIG. 3, the radiation shields 34 are formed with openings 34a through which the posts 35 extend. To maintain the shields vertically spaced with respect to one another, a plurality of cylindrical spacers 37 are received on the posts 35 and positioned between the shields 34. There is an upper set of shields 38 posilines in FIG. l to the dotted position shown in FIG. l,

which may be considered the loading or unloading position. After the carrier 51 has been moved `to the lowermost posit-ion, the platform 43 is easily accessible for loading or unloading parts.

In view of the detailed description included above, the operation of the vacuum furnace should be readily understood. The elevator and sealing mechanism associatedV with the closure member for the vacuum retort provides asimple and easily operated means for facilitating loading and unloading of the furnace. In addition, the burner arrangement utilizing the refractory walls or lining 17 results in a structurally simple means for heating or cooling ,the vacuum retort at a rapid rate.

tioned above the impeller 33b and a lower set of shields i 49 positioned below the impeller 33h. As may best be seen in FIG. 3, each set of radiation shields is carried by a horizontally disposed plate member 39 having a vertical boss 4h extending upwardly at the center thereof in alignment with a hole 39a in the platemember. While the diameter of the boss 40 in the upper set of shields 38 is larger than the diameter of the lower boss, the sets of radiationshields 38 and 49 are otherwiseidentical. Additional spacers 41 are received aroundthe boss 40 and positioned between the radiation shields 34. The use of the spacers 37 and 41 engaging the radiation shields 34 over substantial areas permits the use of a very light stainless steel for theshield material which in one constructed embodiment was only 16 gauge. Without the multiple support provided by the plate 39 and the spacers 37 and 41, there would be a tendency for the shields to deform at the high temperatures to which they are subjected. The upper set of radiation shields` 37 and the While there has been illustrated and described only one form of thel invention, it will be understood that numerous changes `and modifications will occur to those skilled in the art and it is aimed in the appended claims to cover all such changes and modications as fall within the true spirit and scope ofthe present invention.

What is claimed as'new and desired to be secured by Letters Patent of the United States is:

l. A vacuum furnace comprising a, pressure-tight cy-Y lindrical retort supported with the axisthereof extending vertically and having4 a closed upper end and an open lower end, a closure plate for said retort carried by an elevator vertically movable between an upper position in sealingengagement with said open lower end and a low- -v ered position, a plurality of vertically spaced, horizontally isl lower `set 3S are vertically located on the posts 35 by d means of cyindrical spacers 42 which are received on the posts 35 as may best be seen in FIG. 4.

To support parts which are to be heated, there is provided at the upper end of the posts 35 a platform 43 which is generally circular in shape and is horizontally disposed Within the retort 23. The platform has a cylindrical skirt 44 which extends around the outer edge thereof and projects below the level of the platform about twice the distance that it extends above the platform 43. Secured to the lower face of the platform 43 and extending downi Wardly therefrom are six cylindrical'pipe sections 45 which are received on the posts 35 and serve to space the platform 43 above the upper set of radiation shields 38. Secured to the pipe sections 45 and extending radially inwardly therefrom are webs 46 which support at their inner end a circular baffle member 47. The baffle member 47 is intended to prevent radiation downwardly through a center opening 43a inthe platform 43. To support the work above the surface of the platform 43,

there are a plurality of radially extending spacers 48 v 53 which are secured at their upper ends to the compartment'14. To move the carrier 51 between two vertically spaced positions, there are provided `a pair of air cylinders 54 which are located on diametrically opposed sides disposed radiation shields mounted on the upper surface of said closure plate, and a work supporting means carried by said closure plate and positioned above said radiation shields, said work supporting means being spaced below said retort when said elevator is in said lowered position. 2. A vacuum furnace comprising an insulated enclosure having a bottom opening therein, a pressure-tight retor mounted in said enclosure with an open end, extending downwardly through said opening, a closure plate for said retort carried by an elevator vertically movable between an upper position in sealing engagement with said open end of said retort and a lowered position, a fan supported 'on the bottom of said closure plate having an impeller mounted above said plate, radiation shields carried by said closure plate and positioned between said plate and said impeller, a work supporting platform supported by said closure plate and positioned above said impeller, said platform in said lowered position of said elevator being below said retort to permit the loading of parts thereon.

3. A vacuum furnace comprising a pressure-tight retort having an enlarged loading opening in the bottom thereof, a closure plate for said opening carried by an elevator vertically'movable between an upper position in Y sealing engagement with saidopening and a lowered position, resilient sealing means :positioned between said closure plate and said retort, water cooling conduits on said retort to maintain said seal at a low temperature, a plurality of spaced radiation shields carried by said closure plate and positioned to direct the heat in said retort to the upper portion thereof, and a work supporting means carried by said closure plate above said radiation shields, said work supporting means being spaced below said retort when said elevator is in said lowered position. h

4. A vacuum furnace comprising an insulated enclosure of refractory material, a pressure tight cylindrical retort rigidly mounted within said enclosure with the axis thereof extending vertically and having a closed upper end and an open flower end, said enclosurebeing provided with alsdan-5 an opening through Vwhich the lower end of said retort extends, afclolsure plate for said retort carried by an elevator vertically movable between an upperposition in sealing engagement with `said lower end and a lowered position, an air circulation fan carried by said closureV plate includinga motor mounted below said plate and an impeller extendingabove said -plate for insertion into said retort,v gas manifold means for conducting an air-gas mixt ture to the-'outer walls of said refractory enclosure, lsaid,

material being porous with passageways extending therethrough for-saidmixture to enter said enclosure for coml bustion on the inner` wall thereof to heat said pressure tight retort, air'manifolds "for conducting air to Vthe walls otsaid enclosure 'on either side of the wall areas receiving vsaidair-g'as mixture, `said air conducted `to said refractory lwallsy pressurizing the passageways insaid lrefractory wall surrounding said wall areas andpreventing having an open lower end through whichv workA to `be* heat treated may be inserted, a closure plate for said retort carried by an-elevatorvertically Imovable between an` upper position in sealing engagement with said lower end and alowered position, an insulating porous refractory lining for said enclosure 'spaced from the walls of said Vretort, manifolds formed between said non-porous enclosure and said refractory lining, supply means for delivering an air-gas mixture under pressure to said manifolds whereby said mixture lpasses through said porous lining for combustion atthe inner face thereof, air manif-olds positioned n porous enclosureand said refractory lining, and supply UNITED STATES PATENTS 2,289,219 Moran f k .any 14, 1942 v2,388,888 Weller Nov. 13, 1945 2,709,078 Stoddard et al V AMay 24, 1955 2,828,813 Holden '.Apr. 1, 1958 2,869,8564 Greene lan. 20, 1959 2,899,192 Fritz Aug. 11, 1959 2,971,039 Vl/l/esteerl Feb. 7, 1961 3,008,513 Holden NOV. 14, 196.1 v3,020,032 Casey Feb. 6, 1962 3,e27,9375j sobere Apr, 3, 19r2` 3,037,889 Nystrom June 5, 1962 FOREGN PATENTS i Y 501,331 France Apr. 9, 1920 3 t ,sa 1 adjacent said first-mentioned manifold betweenV said nonmeans for delivering .air under pressure to -said air manifolds, said air delivered by said airrnanifolds restricting passageof said air-gas mixture through said lining to a selected area. 'Y

6. The gas fired furnace lof claim `5 including work supporting means carried bysaid closure plate, a plurality of vertically spaced hrorizontally disposed radiation shields positioned between said work supporting means and said closure plate, said work supporting means being spaced below said retort when said elevator is in said lowered position. y

VReierenees Cited in the iile of this patent OTHER REFERENCES Luminous Wall Furnace AHas Versatility,` Article in lndustrial Gas, Volume 38, No. 7,- January 1960, pages 4 6. 

1. A VACUUM FURNACE COMPRISING A PRESSURE-TIGHT CYLINDRICAL RETORT SUPPORTED WITH THE AXIS THEREOF EXTENDING VERTICALLY AND HAVING A CLOSED UPPER END AND AN OPEN LOWER END, A CLOSURE PLATE FOR SAID RETORT CARRIED BY AN ELEVATOR VERTICALLY MOVABLE BETWEEN AN UPPER POSITION IN SEALING ENGAGEMENT WITH SAID OPEN LOWER END AND A LOWERED POSITION, A PLURALITY OF VERTICALLY SPACED, HORIZONTALLY DISPOSED RADIATION SHIELDS MOUNTED ON THE UPPER SURFACE OF SAID CLOSURE PLATE, AND A WORK SUPPORTING MEANS CARRIED BY SAID CLOSURE PLATE AND POSITIONED ABOVE SAID RADIATION SHIELDS, SAID WORK SUPPORTING MEANS BEING SPACED BELOW SAID RETORT WHEN SAID ELEVATOR IS IN SAID LOWERED POSITION. 